Who’s ‘they’? The world is not gonan end on some specific date. We do not know the exact time when the Earth was created and that is an event in the past we are not going to be able to say on eaxactly which date the Earth will cease to exist.
The only point at which Earth will cease to exist is in around 3.5 billion years when the sun has expanded into an orange giant star. Models of the expansion avry slightly but it is possible that Earth will be engulfed by the solar atmosphere. If not at the orange giant stage then when it expands further it is very likely the Earth will be consumed by the sun.
This says nothing of any number of possible events that could trigger a mass-extinction event which could affect all human life on Earth. So the ‘world’ will certainly continue until it is consumed by the planetary nebula and red giant star at the end of the suns life but we do not know about human life. Earth could be struck next March by a large Kuiper Belt object that has been disturbed and is gravitationally falling toward the Sun, wiping out all life on Earth. But Earth would still be here.